|Publication number||US7898710 B1|
|Application number||US 12/623,938|
|Publication date||Mar 1, 2011|
|Filing date||Nov 23, 2009|
|Priority date||Nov 23, 2009|
|Publication number||12623938, 623938, US 7898710 B1, US 7898710B1, US-B1-7898710, US7898710 B1, US7898710B1|
|Inventors||Michael J. Scaggs|
|Original Assignee||Vinyl Technologies, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (6), Referenced by (2), Classifications (8), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
This invention relates, generally, to laser machining. More particularly, it relates to precise removal of thin films in photovoltaic cells.
2. Description of the Prior Art
Galvanometric scanning mirrors and polygon mirrors are well-known.
Conventional methods of removing thin films from photovoltaic cells employ galvanometer based scan mirrors in combination with a scan lens, typically an F-theta lens. Galvanometer scanning mirrors are limited in precision due to the dither of the galvanometer motors. These motors have typical accuracies of less than twenty microradians (20 μrad). A solar panel can be more than five hundred millimeters (500 mm) wide, corresponding to twenty microns (micrometers) (20 μm) for a scan lens having a one thousand millimeter (1000 mm) focal length. The scribe widths in thin film solar cells are less than one hundred microns (100 μm), so it is desirable to have the accuracy of the scribe be less than five percent (5%) of the scribe width. This is not possible with conventional technologies for thin film scribing of large areas.
U.S. Pat. No. 1,735,108 (1929) discloses a combination plano-concave and plano-convex lens pair as an adjustable wedge or prism. U.S. Pat. No. 7,196,831 discloses a counter rotating disk of lenses. The utility of this structure is limited because the lenses add optical power to the system which the design must accommodate. U.S. Pat. No. 5,387,999 discloses a means to control camera shake but has a very limited field of correction and only applies to cameras. U.S. Pat. No. 6,836,364 discloses a rotational means but the fabrication of the optical components is dependent upon selecting glasses with matching densities but with different indices of refraction. This limits the choice of glass and wavelengths to use and may not be suitable for a high power laser scribing application. U.S. Pat. No. 6,320,705 discloses an adjustable wedge that uses a liquid interface for better matching of the optics. A liquid interface cannot be used in high power laser applications and further prohibits high speed scanning. U.S. Pat. No. 4,436,260 discloses an adjustable wedge that uses an air bearing between two optics. The structure lacks utility in high power laser thin film scribing.
The long-standing but heretofore unfulfilled need for a high precision thin film scribing apparatus is now met by a new, useful, and non-obvious invention.
The inventive structure includes a large area scribing system that employs an all refractive scanning means in combination with an F-theta scan lens to produce precision scribes in large area thin films such as a solar photovoltaic cell. A pair of matched lenses which add no detrimental optical power to the scribing lens is configured so one lens is stationary and the other rotated about a common axis to provide a prismatic effect to the incoming light. That light is then directed though an F-Theta scan lens and onto a thin film to selectively remove the film in the fabrication of a solar panel.
More particularly, in the first embodiment, the novel all refractive scanner includes a plano-concave lens element followed by a plano-convex lens element. The glass material, the size and the radius of curvatures of the lenses are selected to establish a particular scan angle. The respective radii of curvature of both elements are matched to cancel out optical power. The plano-concave lens is held stationary while the plano-convex lens element rotates about the axis of its radius of curvature. This causes any incoming light beam to be refracted as if the light were passing through an adjustable optical wedge. The light is refracted over the predetermined scan angle as the plano-convex lens is rotated. When the optic rotates past a particular point where the light can no longer be transmitted, an “off” signal is sent to a laser beam to turn it off until the optic rotates another one hundred eighty degrees (180°) to start scanning again. The panel with the thin film is advanced during the “off” time. The light that passes through the plano-concave/plano-convex lens pair then proceeds to an F-Theta scan lens that focuses the light onto a thin film panel where a scribe is required.
In the preferred embodiment, the plano-convex lens rotates continuously over three hundred sixty degrees (360°) of rotation. However, in lieu of a rotational mounting, a mechanical linkage having a pivot point about the radius of curvature of the lens is moved up and down to provide back and forth scanning using a high precision linear stage. This approach retains the high accuracy but decreases the overall scan speed due to the acceleration and deceleration of the linear stage.
In a second embodiment, the lens combination is optimized for no optical power and one of the two elements is moved in an X and Y fashion to create a decenter of the optic. This decentering causes an angular deviation of the incoming beam which is then directed through an F-Theta scan lens. The field size of this combination is reduced due to the coma and astigmatism introduced by the decentering. These aberrations can be minimized through proper material selection and curvature correction. Precision scanning at the focus of the F-theta lens can be of sub micron precision if a high precision X-Y stage is used where one stage moves one lens in the X direction and the other stages moves the opposing lens in the other, for example.
The primary object of this invention is to reduce the error of the positioning of a scribe line in the production of thin film solar cells where the scan width can be greater than two hundred fifty millimeters (250 mm) for a five hundred millimeter (500 mm) long focal length scan lens.
Another important object is to provide a galvanometric mirror scanner having the ability to scan at higher speeds than traditional galvanometric mirror scanners.
Yet another object is to provide the same angular scan range of conventional galvanometer systems but with higher positional accuracy and faster speeds.
These and other important objects, advantages, and features of the invention will become clear as this description proceeds.
The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts that will be exemplified in the description set forth hereinafter and the scope of the invention will be indicated in the claims.
For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description, taken in connection with the accompanying drawings, in which:
Referring now to
First optical element 12 is a plano-concave, high index glass such as ZnS which is usable from the visible to the far infrared. Second optical element 14 is a plano-convex element having a convex surface identical in radius but of opposite sign relative to first optical element 12. Second optical element 14 rotates about a radius of curvature of first optical element 12 as best understood by comparing
The glass material, the size and the respective radii of curvatures of lenses 12 and 14 are selected to establish a particular scan angle and are matched to cancel out optical power.
Third optical element 16 is an F-theta lens and is depicted as a simple, single element to simplify the drawings. However, in practice, said lens 16 would be two, three, or more elements depending upon the aberration reduction needed.
The light that passes through said three lenses 12, 14, and 16 is focused to a focal spot that lands upon photovoltaic thin film 18. As second element 14 is rotated with respect to first element 12 from the position of
Instead of using mechanical linkage 20 to rotate plano-convex lens 14 about pivot point 22 in a three hundred sixty degree (360°) rotation, a high precision linear stage may be used to accomplish the return to the
Plano-concave lens 30 is moved by a high-precision X-Y stage. Such an X-Y stage, for example, may have a movement of plus or minus ten millimeters (+/−10 mm) with a repeatability of less than one hundred nanometers (100 nm). The scan field may be as large as one hundred fifty millimeters (150 mm). The repeatability of the scan field is the ratio of one hundred nanometers to ten millimeters (100 nm/10 mm) which translates to one and a half microns (1.5μ) over the one hundred fifty millimeters (150 mm) field.
It is therefore understood that the difference between the first and second embodiments is that the second lens rotates with respect to the first in the first embodiment, but is displaced about an X-Y axis in the second embodiment. The effect is the same in both embodiments.
It will thus be seen that the objects set forth above, and those made apparent from the foregoing description, are efficiently attained and since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matters contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention that, as a matter of language, might be said to fall therebetween.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US1735108||Oct 10, 1925||Nov 12, 1929||Cox Multi Color Photo Company||Optical adjusting device|
|US4436260||Dec 21, 1981||Mar 13, 1984||The United States Of America As Represented By The Secretary Of The Air Force||Optical scanner for use in confined areas|
|US5387999||Jun 18, 1993||Feb 7, 1995||Minolta Co., Ltd.||Camera shake compensating optical system|
|US6320705||Jan 8, 1999||Nov 20, 2001||George Dube'||Adjustable optical wedge|
|US6836364||Mar 14, 2003||Dec 28, 2004||Metastable Instruments, Inc.||Beam steering and scanning device|
|US7196831||Aug 9, 2004||Mar 27, 2007||Reliant Technologies, Inc.||Two-dimensional optical scan system using a counter-rotating disk scanner|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US9140833||Apr 15, 2010||Sep 22, 2015||3M Innovative Properties Company||Retroreflective sheeting including a low refractive index layer having a plurality of voids|
|US9291752||Aug 19, 2013||Mar 22, 2016||3M Innovative Properties Company||Retroreflecting optical construction|
|U.S. Classification||359/206.1, 359/210.2, 359/210.1|
|Cooperative Classification||G02B13/0005, G02B26/0875|
|European Classification||G02B13/00A, G02B26/08R|
|Sep 27, 2010||AS||Assignment|
Effective date: 20100924
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:SCAGGS, MICHAEL J.;REEL/FRAME:025043/0863
Owner name: VINYL TECHNOLOGIES, INC. D/B/A VYTEK, INC., MASSAC
|Sep 9, 2014||FPAY||Fee payment|
Year of fee payment: 4
|Sep 9, 2014||SULP||Surcharge for late payment|